1. Technical Field
This disclosure relates to a road surface submergence estimation device that estimates whether the surface of a road, on which a vehicle is traveling, is submerged based on the actual acceleration of the vehicle.
2. Description of Related Art
A road surface (a part of the road) is sometimes submerged with a large amount of rainfall or an inflow of rainwater that falls at other sites. When a vehicle enters a submerged road surface (submerged road), there may be slippage between the wheels of the vehicle and the road surface, or that the engine mounted in the vehicle could stop. To address this problem, a submerged road prediction system is known (for example, see Japanese Patent Application Publication No. 2012-216103 (JP 2012-216103 A)). When a submerged road is included in the traveling route of a vehicle, this system presents the information on a detour to the driver of the vehicle, via the navigation device installed in the vehicle interior, to prompt the driver to travel on a non-submerged road surface (non-submerged road).
A vehicle that uses this submerged road prediction system (hereinafter also called a “system according to the related art”) estimates the amount of precipitation at the position where the vehicle is traveling based on the wiping speed of the wiper on the vehicle and the length of time during which the wiper operates at that speed. In addition, this vehicle sends the estimated amount of precipitation, as well as the position information on the vehicle, to a plurality of other vehicles. At the same time, from each of a plurality of other vehicles, this vehicle receives the estimated amount of precipitation as well as the position information on a vehicle that has sent the estimated amount of precipitation. Each of the vehicles, which use the system according to the related art, determines whether there is a submerged part on the traveling route of the vehicle based on the estimated amounts of precipitation received from the other vehicles traveling ahead on the traveling route.
However, even if the amount of precipitation is the same, the wiping speed of the wiper differs according to the drivers in many cases. In addition, even if the same driver drives the vehicle, the wiping speed of the wiper differs according to the vehicle-driving time zones in many cases. For example, when driving at night, the driver tends to increase the wiping speed of the wiper than when driving at daytime, during which the road surface and the other vehicles can be confirmed easier than at night, even if the amount of precipitation is the same. This means that the amount of precipitation, if estimated based on the wiping speed of the wiper, may include a large error.
In addition, even when the amount of precipitation is small, the surface of a depressed road, such as a road under an overhead crossing or a road under a railroad track, is submerged more easily than the surface of a flat road. Therefore, even if the amount of precipitation can be estimated, it is usually difficult to estimate whether the surface of the road at that point is submerged. Thus, with the system according to the related art, it is difficult to estimate accurately whether the road surface is submerged.